The present invention generally relates to level display devices for audio signals, and more particularly to a level display device for audio signal constructed to display bars having lengths corresponding to the input signal levels on a picture tube.
Generally, when recording an audio signal, there are cases where it is desirable to carry out recording by increasing or decreasing levels in a predetermined frequency band. In addition, when degradation is introduced in the fidelity of a reproduced audio signal in a reproducing apparatus due to effects caused by the frequency characteristics of audio equipments themselves such as speakers and pickup cartridges, the transfer characteristic of a listening room, and the like, there are cases where it is desirable to correct the levels in a predetermined frequency band. Further, there are cases where the frequency characteristic is not made flat during the recording and reproduction, and the frequency characteristic is set to a predetermined characteristic according to the needs. In the above described cases, graphic equalizers capable of variably adjusting the signal level in each of the divided frequency bands are used. When adjusting the level by the graphic equalizer, a level display device is used for displaying the levels throughout the entire band of the input signal and the signal levels in each of the frequency bands.
A conventional level display device was constructed to illuminate a number of light emitting diodes corresponding to the number of input signal levels. Moreover, another conventional level display device was constructed to display bars having lengths corresponding to the input signal levels on a screen of a picture tube.
However, in the above conventional level display devices, numerals for indicating each of the frequency bands, and numerals or scales indicating the level of the signal, are marked on a manipulation panel and the like. Accordingly, there was difference in brightness between the above numerals or scale and the level indication part such as bars displayed on the screen of the picture tube, and there was a disadvantage in that it was difficult to accurately read out the indication visually.
On the other hand, another conventional level display device used comparators for each of the frequency bands, for comparing signals in each of the divided frequency bands with a reference level. This conventional device was disadvantageous in that a substantially large number of comparators were required. Hence, this conventional device had a complex circuit construction, and the cost of the device was inevitably high.
Another conventional level display device could only display one kind of level in real-time, for example. Thus, this conventional device was disadvantageous in that a plurality of kinds of level displays such as in real-time, maximum value, and the like, could not be made, and that the display obtained was inconvenient.